U.S. patent application number 17/294543 was filed with the patent office on 2022-01-27 for dual-flow turbojet engine arrangement with epicyclic or planetary reduction gear.
This patent application is currently assigned to SAFRAN AIRCRAFT ENGINES. The applicant listed for this patent is SAFRAN AIRCRAFT ENGINES. Invention is credited to Julien Fabien Patrick BECOULET, Yanis BENSLAMA, Jeremy DIEVART, Alexandre Jean-Marie TAN-KIM.
Application Number | 20220025821 17/294543 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-27 |
United States Patent
Application |
20220025821 |
Kind Code |
A1 |
TAN-KIM; Alexandre Jean-Marie ;
et al. |
January 27, 2022 |
DUAL-FLOW TURBOJET ENGINE ARRANGEMENT WITH EPICYCLIC OR PLANETARY
REDUCTION GEAR
Abstract
A dual-flow turbojet engine having a central shaft surrounded by
a high-pressure body which rotate about the same longitudinal axis
while being independent in rotation, and including a fan driven by
the central pressure shaft; a high-pressure compressor and a
high-pressure turbine mounted on the high-pressure body; an
inter-turbine casing; a low-pressure turbine mounted on a
low-pressure rotor surrounding the central shaft; an exhaust casing
on which an output cone is mounted; a reduction gear with which the
low-pressure rotor drives the central pressure shaft; two bearings
mounted on the exhaust casing and respectively receiving the
central shaft and the low-pressure rotor; a bearing mounted on the
inter-turbine casing and receiving the low-pressure rotor.
Inventors: |
TAN-KIM; Alexandre Jean-Marie;
(Moissy-Cramayel, FR) ; BENSLAMA; Yanis;
(Moissy-Cramayel, FR) ; DIEVART; Jeremy;
(Moissy-Cramayel, FR) ; BECOULET; Julien Fabien
Patrick; (Moissy-Cramayel, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAFRAN AIRCRAFT ENGINES |
Paris |
|
FR |
|
|
Assignee: |
SAFRAN AIRCRAFT ENGINES
Paris
FR
|
Appl. No.: |
17/294543 |
Filed: |
November 21, 2019 |
PCT Filed: |
November 21, 2019 |
PCT NO: |
PCT/FR2019/052774 |
371 Date: |
May 17, 2021 |
International
Class: |
F02C 7/36 20060101
F02C007/36; F02C 7/06 20060101 F02C007/06 |
Claims
1-9. (canceled)
10. A dual-flow turbojet engine comprising a central shaft
surrounded by a high-pressure spool, coaxial and rotatably
independent, said turbojet engine including from upstream to
downstream according to the direction of circulation of the flow
that passes therethrough when it is operating: a fan driven by the
central shaft; a high-pressure compressor and a high-pressure
turbine belonging to the high-pressure spool; an inter-turbine
casing; a low-pressure turbine; an exhaust casing; said turbojet
engine further including: a low-pressure rotor which surrounds the
central shaft and which comprises the low-pressure turbine; a rotor
upstream journal carried by the inter-turbine casing and which
rotatably guides the low-pressure rotor while being located
downstream of the high-pressure compressor; a rotor downstream
journal carried by the exhaust casing, and which rotatably guides
the low-pressure rotor; a reduction gear through which the
low-pressure rotor drives the central shaft, said reduction gear
being located downstream of the rotor downstream journal; a shaft
downstream journal which rotatably guides the central shaft while
being located downstream of the rotor downstream journal.
11. The turbojet engine according to claim 10, wherein the shaft
downstream journal is carried by the exhaust casing while being
located downstream of the reduction gear.
12. The turbojet engine according to claim 10, comprising a
low-pressure middle journal carried by the inter-turbine casing and
receiving the central shaft.
13. The turbojet engine according to claim 10, comprising an outlet
cone carried by the exhaust casing, and wherein the shaft
downstream journal is located in an inner space of the outlet
cone.
14. The turbojet engine according to claim 13, wherein the
reduction gear is located inside the inner space of the outlet
cone.
15. The turbojet engine according to claim 10, wherein the
low-pressure rotor is equipped with a radially-flexible element
located between the rotor downstream journal and the reduction
gear.
16. The turbojet engine according to claim 10, comprising a
low-pressure compressor driven by the central shaft while being
located between the fan and the high-pressure compressor.
17. The turbojet engine according to claim 10, wherein the
reduction gear is an epicyclic reduction gear comprising: planets
carried by a planet carrier which is carried by the central shaft;
an inner crown which is carried by the low-pressure rotor; an outer
crown which is carried by the exhaust casing; each planet meshing
with the inner crown and the outer crown.
18. The turbojet engine according to claim 10, wherein the
reduction gear is a planetary reduction gear comprising: planets
carried by a planet carrier which is carried by the exhaust casing;
an inner crown which is carried by the low-pressure rotor; an outer
crown which is carried by the central shaft; each planet meshing
with the inner crown and the outer crown.
Description
TECHNICAL FIELD
[0001] The invention relates to a twin-spool turbojet engine
arrangement integrating an epicyclic or planetary reduction
gear.
PRIOR ART
[0002] In such an engine 1 represented in FIG. 1, air is drawn into
an inlet duct 2 to pass through a fan 3 including a series of
rotating blades before being split into a central primary flow and
a secondary flow surrounding the primary flow.
[0003] Afterwards, the primary flow is compressed in compression
stages 4 and 6 before reaching a combustion chamber 7, after which
it expands through a high-pressure turbine 8 and a low-pressure
turbine 9 before being discharged rearwards. In turn, the secondary
flow is propelled directly rearwards by the fan within a flow path
delimited by the casing 11.
[0004] Such a twin-spool type engine includes a so-called
low-pressure spool by which the fan 3 is coupled to the
low-pressure turbine, and a so-called high-pressure spool by which
the compressor is coupled to the high-pressure turbine, these two
spools being coaxial and rotatably independent of each other.
[0005] Thanks to a reduction gear interposed between the
low-pressure turbine and the fan, the low-pressure turbine rotates
faster than the fan driven thereby, in order to increase
efficiency. In this configuration, the low-pressure spool includes
a central shaft for driving the fan and a rotor carrying the
low-pressure turbine while being connected to the central shaft
through the reduction gear.
[0006] The high-pressure and low-pressure spools are held by
journals carried by structural elements of the engine. In practice,
the low-pressure spool is a critical element of the arrangement,
because its central shaft extends substantially over the entire
length of the engine, so that during operation, that is to say when
it rotates, it may be subject to vibration modes that could lead to
the destruction of the engine. In particular, because of its
considerable length, the first flexural vibration mode of the
central shaft lies within its operating range, that is to say
within the range of frequencies corresponding to its rotational
frequencies.
[0007] This situation requires carrying out a high-speed balancing
of the central shaft, but also providing for journals that are
capable of damping its vibration modes to limit possible
imbalances. Such journals, generally referred to by the acronym SFD
meaning "squeeze film dampers" include a fixed soft cage carrying a
bearing receiving the low-pressure spool, and around which a
hydraulic pressure is maintained, this journal type being expensive
to implement.
[0008] The invention aims to provide arrangement solutions allowing
improving holding of the low-pressure rotating elements to limit
resort to complex journals for damping vibration modes.
DISCLOSURE OF THE INVENTION
[0009] To this end, an object of the invention is a dual-flow
turbojet engine including a central shaft surrounded by a
high-pressure spool, coaxial and rotatably independent, this
turbojet engine including from upstream to downstream according to
the direction of circulation of the flow that passes therethrough
when it is operating: [0010] a fan driven by the central shaft;
[0011] a high-pressure compressor and a high-pressure turbine
belonging to the high-pressure spool; [0012] an inter-turbine
casing; [0013] a low-pressure turbine; [0014] an exhaust
casing;
[0015] this turbojet engine further including: [0016] a
low-pressure rotor which surrounds the central shaft and which
comprises the low-pressure turbine; [0017] a rotor upstream journal
carried by the inter-turbine casing and which rotatably guides the
low-pressure rotor while being located downstream of the
high-pressure compressor; [0018] a rotor downstream journal carried
by the exhaust casing, and which rotatably guides the low-pressure
rotor; [0019] a reduction gear through which the low-pressure rotor
drives the central shaft, this reduction gear being located
downstream of the rotor downstream journal; [0020] a shaft
downstream journal which rotatably guides the central shaft while
being located downstream of the rotor downstream journal.
[0021] With this arrangement, the speed of the central shaft is
reduced and its length is enlarged thanks to the shaft journal
located downstream, which helps reducing the frequencies of its
normal modes to bring them away from the rotational frequencies.
The reduction of this speed also allows enlarging the fan diameter
without the tip speed of the blades of this fan becoming
excessive.
[0022] The invention also relates to a turbojet engine as defined,
wherein the shaft downstream journal is carried by the exhaust
casing while being located downstream of the reduction gear.
[0023] The invention also relates to a turbojet engine as defined,
comprising a low-pressure middle journal carried by the
inter-turbine casing and rotatably guiding the central shaft.
[0024] The invention also relates to a turbojet engine as defined,
comprising an outlet cone carried by the exhaust casing, and
wherein the shaft downstream journal is located in an inner space
of the outlet cone.
[0025] The invention also relates to a turbojet engine as defined,
wherein the reduction gear is located inside the inner space.
[0026] The invention also relates to a turbojet engine as defined,
wherein the low-pressure rotor is equipped with a radially-flexible
element located between the rotor downstream journal and the
reduction gear.
[0027] The invention also relates to a turbojet engine as defined,
including a low-pressure compressor driven by the central shaft
while being located between the fan and the high-pressure
compressor.
[0028] The invention also relates to a turbojet engine as defined,
wherein the reduction gear is an epicyclic reduction gear
comprising: [0029] planets carried by a planet carrier which is
carried by the central shaft; [0030] an inner crown which is
carried by the low-pressure rotor; [0031] an outer crown which is
carried by the exhaust casing; [0032] each planet meshing with the
inner crown and the outer crown.
[0033] The invention also relates to a turbojet engine as defined,
wherein the reduction gear is a planetary reduction gear
comprising: [0034] planets carried by a planet carrier which is
carried by the exhaust casing; [0035] an inner crown which is
carried by the low-pressure rotor; [0036] an outer crown which is
carried by the central shaft; [0037] each planet meshing with the
inner crown and the outer crown.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a longitudinal sectional view of a known dual-flow
twin-spool turbojet engine;
[0039] FIG. 2 is a schematic longitudinal sectional view of a
turbojet engine architecture according to the invention;
[0040] FIG. 3 is a schematic longitudinal sectional view of a
downstream portion of a turbojet engine architecture according to a
first embodiment of the invention;
[0041] FIG. 4 is a schematic longitudinal sectional view of a
downstream portion of a turbojet engine architecture according to a
second embodiment of the invention;
[0042] FIG. 5 is a schematic longitudinal sectional view of a
downstream portion of a turbojet engine architecture according to a
third embodiment of the invention;
[0043] FIG. 6 is a schematic longitudinal sectional view of a
downstream portion of a turbojet engine architecture according to a
fourth embodiment of the invention;
[0044] FIG. 7 is a schematic longitudinal sectional view of a
downstream portion of a turbojet engine architecture according to a
fifth embodiment of the invention.
DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS
[0045] As schematically represented in FIG. 2, the engine according
to the invention features an architecture comprising a fan 13 at
its upstream portion AM followed by a low-pressure compressor 14.
The fan and the low-pressure compressor are driven in rotation by a
central shaft AC extending over most of the length of the engine,
the fan being crossed by the entirety of the flow coming inside
this engine.
[0046] The upstream AM and downstream AV directions are defined
with respect to the direction of circulation of the flow in the
engine along its longitudinal axis AX, in accordance with usual
conventions.
[0047] A high-pressure compressor 16 located immediately downstream
AV of the compressor 14 compresses the fluid of the primary flow
having passed through the low-pressure compressor, before getting
in a non-represented combustion chamber located immediately
downstream of this high-pressure compressor 16.
[0048] After passage in the combustion chamber, the fluid expands
through a high-pressure turbine 17 which drives the compressor 16.
The blades of the high-pressure compressor 16 and of the
high-pressure turbine 17 are carried by the same high-pressure
spool CH or are integrally made with the latter. This high-pressure
spool CH extends in the central region of the engine along the axis
AX, it surrounds the central shaft AC while being fully rotatably
independent thereof.
[0049] After having passed through the high-pressure turbine 17,
the fluid transits in an inter-turbine casing bearing the reference
numeral 18 in FIG. 3, before passing through a low-pressure turbine
19, and is then discharged through an exhaust casing 21.
[0050] The inter-turbine casing 18 includes concentric outer shroud
and inner shroud delimiting therebetween an annular space for the
passage of the primary flow, as well as a set of fixed radial
blades each linking the outer shroud to the inner shroud and
allowing de-twisting the primary flow. Similarly, the exhaust
casing 21 includes concentric outer shroud and inner shroud
delimiting an annular space for the passage of the expanded primary
flow, as well as a set of fixed radial arms each linking these two
shrouds to each other.
[0051] The low-pressure turbine 19 is rotatably linked to the
central shaft by an epicyclic reduction gear 22 located downstream
AV, and thanks to which it rotates faster than the fan 13, in order
to improve the efficiency of the engine.
[0052] As shown more clearly in FIG. 3, the exhaust casing 21
carries an outlet cone 23 which closes the downstream region of the
engine located radially inward of the primary flow path, this
outlet cone 23 extending downstream.
[0053] The reduction gear 22 is located inside an inner space E
delimited by the exhaust casing 21 and by the outlet cone 23
extending this casing 21, while being connected to the central
shaft AC and to a rotor RB carrying the low-pressure turbine.
[0054] This rotor RB which surrounds the central shaft AC extends
from a middle portion by which it carries the disks or blades of
the low-pressure turbine, up to a downstream portion by which it is
coupled to the reduction gear. This rotor RB includes in its
central region a radially-flexible element 24.
[0055] This flexible element 24 is soft according to the radial
direction to enable off-centring of the upstream portion of the
rotor RB with respect to its downstream portion while ensuring a
torque transmission from one portion to another.
[0056] As shown in FIG. 3, the low-pressure rotor RB is held and
rotatably guided by an upstream journal 26 located upstream of the
low-pressure turbine 19 and by a downstream journal 27 located
between this low-pressure turbine 19 and the radially-flexible
element 24. The rotor upstream journal 26 is carried by the
inter-turbine casing 18, and the rotor downstream journal 27 is
carried by the exhaust casing 21. At least one of the two rotor
journals 26 and 27 is a thrust journal, that is to say taking up
the axial thrust force generated by the low-pressure turbine to
transfer it to the structure of the engine.
[0057] This reduction gear includes planet pinions 28 surrounding
an inner crown 29, also called sun wheel, and surrounded by an
outer crown 33 each meshing with these two crowns, these pinions 28
being carried by a planet carrier 32.
[0058] In the case of FIG. 3, the reduction gear, which bears the
reference numeral 22, is of the epicyclic type, that is to say the
planet carrier 32 is rotatably movable while being rigidly secured
to the central shaft AC. In turn, the inner crown 29 is rigidly
secured to the low-pressure rotor RB whereas the outer crown 33 is
rigidly secured to the exhaust casing 21 while being carried by the
latter.
[0059] The central shaft AC is carried and rotatably guided by an
upstream journal that is not shown in FIG. 3 and located at the
upstream portion of the engine, and by a central shaft downstream
journal 34 which is located downstream of the reduction gear 22,
while being carried by the exhaust casing 21. As shown in the
figures, the downstream journal 34 is located in an inner space E
of the outlet cone 23.
[0060] Holding of the central shaft AC may be improved by providing
for a low-pressure middle journal 36, as represented in FIG. 4,
this middle journal being carried by the inter-turbine casing 18
and receiving the central shaft AC to support its middle region.
The addition of this middle journal 36 allows enhancing holding of
the central shaft AC so as to further reduce the frequencies of its
vibration modes.
[0061] The examples of FIGS. 5 and 6 show embodiments having,
respectively, the same architectures as in FIGS. 3 and 4, but
wherein the reduction gear, bearing the reference numeral 22', is a
planetary, rather than epicyclic, reduction gear.
[0062] This planetary reduction gear 22' also includes planet
pinions 28 surrounding an inner crown 29 and surrounded by an outer
crown 33 while each of them meshes with these two crowns, these
pinions 28 being carried by a planet carrier 32'.
[0063] The planet carrier, bearing the reference numeral 32', is
fixed while being carried by the exhaust casing 21, and the outer
crown 33 is movable while being rigidly secured to the central
shaft AC. In turn, the inner crown 29 is carried by the
low-pressure rotor RB, like in the embodiments of FIGS. 3 and
4.
[0064] Thus, in the example of FIG. 5, the central shaft is held by
an upstream journal that is not shown and by the downstream journal
34, and in the example of FIG. 6, this shaft AC is held by the
downstream journal 34 and also by a low-pressure middle journal,
these two journals having the same arrangement as in the already
described examples of FIGS. 3 and 4.
[0065] In the embodiments of FIGS. 2 to 6, the central shaft
downstream journal 34 is a fixed journal carried by the exhaust
casing 21 while being located downstream of the reduction gear 22
or 22'. Complementarily, or alternatively as represented in FIG. 7,
the shaft downstream journal, bearing the reference numeral 34',
may be an inter-shaft journal, which surrounds the shaft AC to hold
it and rotatably guide it, while being surrounded by the rotor RB,
and while being located downstream of the downstream rotor journal
27. In this configuration, the downstream portion of the central
shaft AC is thus held via the low-pressure rotor RB, and not
directly by the exhaust casing 21.
[0066] The invention allows getting rid of the additional journals
usually provided to support the central shaft in order to bring the
natural frequencies of this shaft off its rotational frequencies.
Thus, it allows limiting the implementation of complex journals
such as SFD journals, and reducing the balance accuracy required
for the central shaft.
* * * * *